Welcome to the Corvette Forums at the Corvette Action Center!

Transmission Leak



My 1981 has a weird transmission leak. It slow drips from the speedo cable connection, but only if it sits for a week without being driven. If I drive it regular, it doesn't leak. Its driving me crazy. Anybody got any ideas why it leaks, its as tight as i can get it, and why doesn't it leak if I drive it regularly?


Well-known member
Nov 11, 2004
Old Fort NC/Vero Beach FL
03 Z-51,78 L82 Coupe
Put a New O-Ring in the speedo gear housing!!! About $0.50 for th O-Ring and 15 min to install!!!While your at it change the one on the end of the Dip Stick tube,it will next!!!:upthumbs PS The dip stick 0-ring is allot more fun!!!!!:boogie :cool


There is a fitting going into the transmission where the speedometer cable is attached to, it’s called the speedometer driven gear fitting. Automatics and Manual transmissions have them but they differ a little I think it is the cup seal depth. On the outer diameter of the gear fitting there is an “O” ring and inside there is a cup seal pressed in. May be one or both, my story was a little different.
A couple of years ago mine also leaked no mater how tight the cable was. I pulled the driven gear fitting and saw that the cup seal was broken so I replaced it. Well that didn’t cure the problem. I pulled the driven gear fitting again and noticed that the speedometer gear shaft had wobbled out the inside diameter of driven gear fitting. The original driven gear fitting on mine was cast aluminum. So I ordered from the Dealer, a new driven gear fitting, comes with inner cup seal. A new “O” ring for the outer seal and a new speedometer gear will have to be ordered as well. If I remember correctly total from dealer was $19.00 for all three parts.
If you do have to replace the driven gear fitting make note to read instructions as to where the depth of the inner cup seal is pressed to as there is a difference in automatic depth or manual transmission depth of the seal.
Here is what the driven gear fitting looks like:http://www.ecklers.com/product.asp?pf_id=45170&dept_id=1873
Hope this helps,

Corvette Forums

Not a member of the Corvette Action Center?  Join now!  It's free!

Help support the Corvette Action Center!

Supporting Vendors


MacMulkin Chevrolet - The Second Largest Corvette Dealer in the Country!



Advertise with the Corvette Action Center!

Double Your Chances!


Top Bottom